Process for effecting coupling reactions



Patented Jan. 22, 1952 PROCESS FOR EFFECTING COUPLING REACTIONS Peter Pieth, Basel, switzerlaniassignor to Ciba Limited, Basel, Switzerland, a. Swiss firm No Drawing. Application February 25, 1948, Se-

rial No. 10,906. In Switzerland November 28,

Section 1, Public Law 690, August 8, 1946 Patent expires November 28, 1965 3 Claims. (01. 260-197) It is well known that ortho-hydroxydiazo compounds are comparatively stable and as a rule can stand rather severe conditions of coupling without undue decomposition occurring.

However, there are some coupling reactions which hitherto could not be carried out in a satisfactory manner because there were always losses without an obvious cause.

It has now been found that coupling reactions between ortho-hydroxydiazo compounds and 1z5 dihydroxynaphthalenes are carried out with advantage in a medium containing naphthalene sulfonic acid salts.

As ortho-hydroxydiazo compounds according to the present process, any diazotized ortho-hydroxyamino-aryl-compound, for instance, of the benzene series, may be used. The said orthohydroxydiazo compounds may contain further substituents such as are usual in azo dyestufi's, for instance, nitro and sulfonic acid groups, halogen atoms, etc. Particular mention may be made of diazotized Z-amino-1-hydroxybenzene-4-sulionic acid and diazotized 2-amino-l-hydroxy-4- chlorobenzene-6-sulfonic acid. With particular advantage the present process may be applied to the coupling of lrfi-dihydroxynaphthalenes which are free from sulfonic acid groups, for instance, 125-dihydroxy naphthalene itself, without any further substituents.

According to the present invention the coupling reaction is carried out in a medium containing, of course, the components taking part in the coupling reaction, the alkali necessary for the coupling reaction, and, in addition, naphthalene sulfonic acid salts. useful to add a naphthalene sulfonic acid either to the diazo compound or, if desired, to the orthohydroXyamino-aryl compound before diazotizing' is effected. In many instances a crude naphthalene sulfonic acid solution, obtained by the sulazctization mixture, the corresponding naphthalene sulfonic acid salts will be formed anyway.

The coupling reaction can be carried out, under conditions otherwise usual, in a medium containing a suitable alkali, for instance an alkali metal carbonate or an alkali metal hydroxide.

In many cases it is i Depending on the particular circumstancescou-t pling may be effected at a relatively low temperature (between Oand 5 C.), or at room tem: perature, or even at a raised temperature. If desired, the temperature may be raisedjduring the coupling reaction.

It is a feature of the present process that an improvement is brought about in the yield and/or the purity of the dyestufi.

Example 1 37.8 parts of Z-amino-1-hydroxybenzene-4 sulfonic acid are dissolvedin parts-oi water with the addition of such an amount of sodium carbonate that a feeble alkaline reaction ensues. 75 parts by volume of a crude solution of naphthalene sulfonic acid of about 30% strength are added, which is obtained by diluting a reaction mass containing mostly naphthalene-l-sulfonic acid and prepared by direct sulfonation oi naphthalene. The reaction mixture is cooled to 5 C. by an addition of ice, then 13.8 parts of solid sodium nitrite are added in small portions and the whole is stirred for 5 hour. If the reaction mixture happens to contain free nitrous acid a small amount of 2'-amino-l-hydroxybenzenelsulfonic acid is added.

32 parts of 1:S-dihydroxynaphthalene in the form of a finely'ground aqueous paste of about 30% strength is added to the reaction mixture containin the diazo compound mentioned above. By addition of 300 parts of ice the whole is cooled down to about 0 0., 109 parts of caustic soda solution of 30% strength are then added as a single addition and the whole is stirred for 2 hours at 02 C. After coupling is finished the dyestufi solution is neutralized by means of 92 parts of concentrated hydrochloric acid, warmed to 50 C. and the dyestuff is precipitated by the addition of parts of sodium chloride. After stirring for some time the dyestufi of the formula dyestuff described in U. S. Pat. No. 722,715 is obtained in substantially increased yield.

Example 2 44.7 parts of 2-amino-1hydromr-i-chlorobenzene-fi-sulfonic acid-in the form of a paste feebly acid with sulfuric acid are stirred with 100 parts of water-. 70 parts by volume of a naphthaleneqesulfonica' acid solution; of 30 strength" (see'EXample 1) are added and'the'reaction mixture is cooled to 3 C. by the addition trous acid is present and the whole is stirred.

for V; hour. Any excess ofnitrous acid is re- 4 naphthalene in an aqueous alkaline medium containing an alkali metal salt of naphthalene-1- sulfonic acid.

-2.' In; the process for coupling": diazotized V 2- amino" 1' -'hydroxybenzene"- 4 sulfonic movement which consists in reacting the said moved by the addition. of'a' smallp artt'ofther' amine mentioned above. Then32'parts"of 1":5- dihydroxynaphthalene as a-finelyrground aquee ous paste of about 30% strength'iares adddtaandi the reaction mixture is cooled to 0 C. by the addition of 100 parts of ice. Then 1.00,parts of.. caustic soda solution of 30% strengtli-areeaddedl as a single additionand the whole is stirred at 0-2 C. When thecoupling reaction issfi'nished. the dyestufi solution is neutralized by means'of 80ilpartsiofzconcentrated-uhydrochloricv acid: The: whole iszwarmedup to. 50? C..and;.thevdyes'tufl'z; is: precipitated :by, the :addition: of; 180; parts; of sodiunrehlorides. Aiter cooling down to;25. 'Clthei dyestufi isi-filtered and driedaat809 0. invacuo:

What I claim is:

1. In the: process-"for:- couplinga a member selectediifrom the group:.= -consistin ofdiazotizedi 2 amino 1 hydrdxybenzene -4rsulfoni'c 'ac-i'd:

zene-G-sulfonic acid. with LS-dihydrOXynaphthalene; the;improvement' -whichconsists in reacting. the'fisaid member and the" 1,5 dihydroxy' and diazotized 2-aminoel-hydroxyl-chlorobendiazotized'. 2":---amino l hydroxybenzene 4- sul-fonic acid and the 1,5-dihydroxynaphthalene 'inan' aqueous, alkaline medium containing an alkali "metalxsalt .of 'naphthalene-l-sulfonic acid.

31 Iii the process for coupling diazotized 2. .-:.--amino .-=-l-'-hydroxy 4 chlorobenzene 6- 'sulfonic" acid with" :1,5-dihydroxynaphthalene, the improvement whicli consists in reacting the said diazotized. 2 .-amino 1 hydroxy 4 chloroli'enzene fisulfonic acid and the 1,5-dihydroxynaphthalene in an aqueous alkaline medium containing: an alkali metal salt of naphthalene-lsulfonic acid.

PETEBBIETHZ.

REFERENCES CITED" The following references are of recordilinetlfe file. offthis patent:

UNITED "STATESt -PATENTS Number Name Date 722,715 Kahn Mari 17, 1903 726,695 Kahn Apr. 281.1903

1,629,906 Montmolli'rretall May2411927 1,847,650 Immerheiser 'etia'l. Mar. 1'; 1932" 

1. IN THE PROCESS FOR COUPLING A MEMBER SELECTED FROM THE GROUP CONSISTING OF DIAZOTIZED 2-AMINO-1-HYDROXYBENZENE-4-SULFONIC ACID AND DIAZOTIZED 2-AMINO-1-HYDROXY-4-CHLOROBENZENE-6-SULFONIC ACID WITH 1,5-DIHYDORXYNAPHTHALENE, THE IMPROVEMENT WHICH CONSISTS IN REACTING THE SAID MEMBER AND THE 1,5-DIHYDROXYNAPHTHALENE IN AN AQUEOUS ALKALINE MEDIUM CONTAINING AN ALKALI METL SALT OF NAPHTHALENE-1SULFONIC ACID. 